Question:  How long does the battery on this watch last? 

Answer: There is no battery. Its entirely mechanical. For the price, I was skeptical about the self-winding mechanism. However, I can wear this watch for an entire day and it will self-wind itself without me touching it. If I leave it off my wrist for more than 8 to 10 hours, that's typically when I have to wind it. Like all mechanical watches, do not overwind it.